From: Srivatsa Vaddagiri Date: Fri, 17 Mar 2006 07:04:06 +0000 (-0800) Subject: [PATCH] x86: check for online cpus before bringing them up X-Git-Tag: v2.6.16~14 X-Git-Url: http://www.pilppa.org/gitweb/gitweb.cgi?a=commitdiff_plain;h=82c3c03a4096badd026c6e337f3c5dde020e9ec6;hp=8532159f5521ba24e697f0d25970ae89ff62a1f2;p=linux-2.6-omap-h63xx.git [PATCH] x86: check for online cpus before bringing them up Bryce reported a bug wherein offlining CPU0 (on x86 box) and then subsequently onlining it resulted in a lockup. On x86, CPU0 is never offlined. The subsequent attempt to online CPU0 doesn't take that into account. It actually tries to bootup the already booted CPU. Following patch fixes the problem (as acknowledged by Bryce). Please consider for inclusion in 2.6.16. Check if cpu is already online. Signed-off-by: Srivatsa Vaddagiri Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/arch/i386/kernel/smpboot.c b/arch/i386/kernel/smpboot.c index eba7f53f8b4..7007e178379 100644 --- a/arch/i386/kernel/smpboot.c +++ b/arch/i386/kernel/smpboot.c @@ -1029,6 +1029,16 @@ int __devinit smp_prepare_cpu(int cpu) int apicid, ret; lock_cpu_hotplug(); + + /* + * On x86, CPU0 is never offlined. Trying to bring up an + * already-booted CPU will hang. So check for that case. + */ + if (cpu_online(cpu)) { + ret = -EINVAL; + goto exit; + } + apicid = x86_cpu_to_apicid[cpu]; if (apicid == BAD_APICID) { ret = -ENODEV;